The pathogenesis of lung ischemia reperfusion injury (IRI) has historically been characterized by the recruitment and extravasation of neutrophils. However, more recent studies have suggested a role for natural killer T-cells (NKT) in the pathogenesis of this injury. Agonists of the anti-inflammatory Gs-coupled adenosine A2A receptor (A2AR) have been shown to inhibit the activity of most inflammatory cells, and extensive preclinical evidence exists for their use in prevention of acute ischemia reperfusion. Importantly, IRI is a significant risk factor for the development of chronic allograft rejection, bronchiolitis obliterans (BO). Evidence supports alloimmune-dependent and alloimmune-independent factors in the etiology BO. More recently activation of A2ARs on lymphocytes and antigen presenting cells have been shown to attenuate the alloimmune response. Additionally A2AR stimulation and upregulation on lymphocytes promotes peripheral tolerance by inducing T-cell anergy. Currently little is known about the role of A2AR agonists in lung transplant rejection. Our overall hypothesis is that A2AR signaling is critical in modulating the innate and adaptive immune responses relevant to the pathogenesis of BO. Aim 1: Will determine, using an in-vivo lung IRI model, if A2AR signaling specifically on NKT cells confers protection from lung IRI. Aim 2: Will determine, using a non-revascularized heterotopic tracheal model and genetically modified mice strains, the importance and cellular mechanisms of A2AR signaling in the pathogenesis of BO. Aim 3: Will determine if A2AR signaling can be used to promote the development of a tolerant state. Also addressed will be ways to effectively introduce A2AR agonists with standard immunosuppression regimens. This grant encompasses a training program for the PI which includes coursework plus frequent interactions with mentors and advisors. With the guidance of the candidate's advisory committee and the institutional support provided by the University of Virginia's Department of Surgery, the candidate will development the skills required to evolve into an independent investigator. RELEVANCE (See instructions): BO remains the major hurdle to long-term survival in lung transplant recipients. There currently are no uniformly consistent strategies to prevent/treat BO. IRI is a significant risk factor for BO. Given the anti- inflammatory and immunomodulating effects of A2ARs, strategies utilizing A2AR agonists may be uniquely suited to prevent both the alloimmune-independent and alloimmune-dependent factors involved in BO.